The present invention relates to a semiconductor device, as well as a manufacturing method therefor, in which semiconductor switching elements constituting a logic circuit area and semiconductor storage elements constituting a storage area are compositely mounted on one substrate.
The present invention also relates to portable electronic equipment and an IC card each provided with such a semiconductor device.
FIG. 1 shows a structural sectional view of a common flash memory. A floating gate 106 made of polysilicon is provided on a P-type well region 101 via a first oxide 104, and a control gate 107 made of polysilicon is provided on the floating gate 106 Via a second oxide 105. On a surface of the P-type well region 101 on both sides of the gate electrodes 106, 107 are formed a first N-type diffusion region 102 and a second N-type diffusion region 103. End portions of the gate electrodes 106, 107 are overlapped with end portions of the first N-type diffusion region 102 and the second N-type diffusion region 103, respectively.
As one mode of the composite mounting of a flash memory and logic circuits, there is also a known technique that memory cells are arranged in an array configuration while, on peripheries of the array, logic circuits serving as peripheral circuits such as a decoder, write/erase circuits and a read circuit are disposed.
There is further a known technique that a logic circuit unit such as MPU (Micro-Processing Unit), an SRAM (Static RAM) unit for use as cache, and the like are provided in order that a memory unit functions as an information processing system for personal computers, portable telephones and the like.
Conventionally, manufacturing a semiconductor device in which a flash memory and logic circuits are compositely mounted would inevitably involve a large extent of cost increase. As to the reason of an increase in manufacturing cost which accounts for the overall cost increase, the composite mounting makes the process more complex, giving rise to a necessity for additional masks. For example, with a flash memory, because of the necessity for two polysilicon layers for memory elements and other reasons, seven to eight masks would have to be added to a standard CMOS manufacturing process.